RUST-36 Support of Decimal128 type

[zonyitoo]

According to BSON 1.1 Spec, it introduced a new type decimal128.

But currently Rust doesn't support d128 type natively.

Related links

1. d128 crate: https://github.com/alkis/decimal
2. Official support RFC: Add a BigDecimal type rust-num/num#8

[zonyitoo]

Thoughts? @kyeah

[kyeah]

nice, just one comment; looks great otherwise.

[saghm]

I believe crates.io doesn't let you publish a crate that has both git and crates.io dependencies. Is there any chance that the author of the decimal crate might accept a PR?

EDIT: Oops, that was the "one comment"; never mind!

[zonyitoo]

I have already submitted a PR to alkis/decimal#23 . I will remove that git dep after this PR is accepted.

[lrlna]

I see there is a commit with decimal128 support already. Are you still thinking of merging that commit in? Would love to see that happen!

[zonyitoo]

Don't know if it is the best way to support decimal 128 in Rust, yet.

Rust is now supported i128 and u128. Maybe in the future it will support d128?

[lrlna]

@zonyitoo by the best way do you mean you're not sure if using the decimal crate is a good idea, or is this more about whether the support is up to the spec?

it's possible core will support d128, but I feel like that might be a long way off :(. In the meantime would be cool to have a workaround \o/

[zonyitoo]

Yes, I agree. I would take sometime to make this commit works with the master.

[lrlna]

@zonyitoo if you feel like it's more work than you have capacity for, I can also help out! I just didn't want to step on your toes, since there was already a commit going.

[zonyitoo]

@lrlna That would be great! I don't have spear time in the recent future :(